Preimaginal Conditioning Research Articles

Spodoptera cosmioides (Lepidoptera: Noctuidae) as an alternative host for mass rearing the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

Abstract Different alternative hosts can reduce or even avoid pre-imaginal conditioning of parasitoids in mass production programs. Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) may be an alternative host for mass rearing the parasitoid Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae). The objective of this study was to evaluate the parasitism, emergence, egg-to-adult period, progeny size, sex ratio, and consumption of host tissue per individual of P. elaeisis produced using S. cosmioides pupae in the laboratory. Newly formed S. cosmioides pupae were weighed, individualized in glass tubes and each one was exposed to six newly emerged P. elaeisis females during 48 h. These pupae were transferred to plastic pots until the emergence of P. elaeisis adults. Palmistichus elaeisis parasitized and emerged from 100.0 % and 87.5 % of the S. cosmioides pupae, respectively. The egg-to-adult period of P. elaeisis was 24.28 ± 0.18 days, with 109 ± 2 individuals emerging per host pupae. Mass consumption of the host was 2.56 ± 0.01 mg per parasitoid emerged. This is the first report of P. elaeisis parasitizing and developing in S. cosmioides pupae. The ease of rearing S. cosmioides with an artificial diet, and the high parasitism, emergence, and progeny size of P. elaeisis support the suitability of this alternative host to mass-rearing this parasitoid.

Host Choice and Feeding Behaviours of Glossina morsitans Offspring Whose Parents Were Fed on Different Host Species

The success of any tsetse control program depends on the knowledge of their behaviour. This study assessed the host choice and feeding behaviours of Glossina morsitans siblings whose parents were bloodfed on rabbits, guinea pigs, rodents, and squirrels. Each individual host was placed in a screen cage, which allowed flies to enter through openings on each side. The groups of flies (20 per replicate), which were colour-marked differently based on their parents’ blood meal hosts, were released from the centre of large semi-field cage. The released flies were aspirated after 24 h and then sorted based on their location, feeding status, and parents’ blood meal. A total of 213 flies (72.95% of those recovered) were attracted to the hosts. The numbers of flies attracted to different hosts varied significantly (χ24 = 33.685, p = 0.0001): rodents (n = 80, p = 0.006), rabbits (n = 59, p = 0.331), guinea pigs (n = 49, p = 0.057), and squirrels (n = 25, p = 0.005). The numbers of flies attracted to their parent’s blood meal source varied significantly (χ212 = 56.476, p < 0.001): rabbits (n = 35, 59.32%, p < 0.001), rodents (n = 25, 31.25%, p = 0.043), and guinea pigs (n = 19, 38.78%, p = 0.45). But only 39 flies (18.31% of the total attracted) bloodfed on the hosts, including guinea pigs (n = 10, 25.64%), rodents (n = 23, 58.97%), rabbits (n = 6, 15.38%), and squirrels (n = 0, 0.0%). There was significant variation in the number of flies that fed successively across hosts (χ24 = 49.478, p < 0.001). The findings from this study confirm the presence of differential attractiveness of the hosts to flies and the so-called “Hopkins host selection principle” or “pre-imaginal conditioning”. Therefore, the study attracts the need for detailed investigation on the influence of blood meal sources on tsetse fly siblings’ behaviours across filial generations using small mammals or other large mammal species.

Drosophila Free-Flight Odor Tracking is Altered in a Sex-Specific Manner By Preimaginal Sensory Exposure.

In insects such as Drosophila melanogaster, flight guidance is based on converging sensory information provided by several modalities, including chemoperception. Drosophila flies are particularly attracted by complex odors constituting volatile molecules from yeast, pheromones and microbe-metabolized food. Based on a recent study revealing that adult male courtship behavior can be affected by early preimaginal exposure to maternally transmitted egg factors, we wondered whether a similar exposure could affect free-flight odor tracking in flies of both sexes. Our main experiment consisted of testing flies differently conditioned during preimaginal development in a wind tunnel. Each fly was presented with a dual choice of food labeled by groups of each sex of D. melanogaster or D. simulans flies. The combined effect of food with the cis-vaccenyl acetate pheromone (cVA), which is involved in aggregation behavior, was also measured. Moreover, we used the headspace method to determine the "odorant" identity of the different labeled foods tested. We also measured the antennal electrophysiological response to cVA in females and males resulting from the different preimaginal conditioning procedures. Our data indicate that flies differentially modulated their flight response (take off, flight duration, food landing and preference) according to sex, conditioning and food choice. Our headspace analysis revealed that many food-derived volatile molecules diverged between sexes and species. Antennal responses to cVA showed clear sex-specific variation for conditioned flies but not for control flies. In summary, our study indicates that preimaginal conditioning can affect Drosophila free flight behavior in a sex-specific manner.

Pre-imaginal conditioning alters adult sex pheromone response in Drosophila.

Pheromones are chemical signals that induce innate responses in individuals of the same species that may vary with physiological and developmental state. In Drosophila melanogaster, the most intensively studied pheromone is 11-cis-vaccenyl acetate (cVA), which is synthezised in the male ejaculatory bulb and is transferred to the female during copulation. Among other effects, cVA inhibits male courtship of mated females. We found that male courtship inhibition depends on the amount of cVA and this effect is reduced in male flies derived from eggs covered with low to zero levels of cVA. This effect is not observed if the eggs are washed, or if the eggs are laid several days after copulation. This suggests that courtship suppression involves a form of pre-imaginal conditioning, which we show occurs during the early larval stage. The conditioning effect could not be rescued by synthetic cVA, indicating that it largely depends on conditioning by cVA and other maternally-transmitted factor(s). These experiments suggest that one of the primary behavioral effects of cVA is more plastic and less stereotypical than had hitherto been realised.

Is It Possible to Manipulate Scelionidae Wasps' Preference to a Target Host?

Parasitoid host selection is mainly mediated by chemical cues, which can be adjusted by experience, changing their innate behavior. Therefore, this study evaluated if immature experience (pre-imaginal conditioning) on eggs and volatiles from different host eggs has influence on parasitism and chemotaxic behavior of Telenomus podisi Ashmead and/or Trissolcus basalis Wollaston (Hymenoptera: Scelionidae). Both wasp species were submitted to a multiple-choice parasitism test among Euschistus heros (Fabricius), Piezodorus guildinii (Westwood), and Nezara viridula L. (Hemiptera: Pentatomidae) (Hemiptera: Pentatomidae) egg masses. Eggs from these three stink bugs were equally offered to female parasitoids. After that, adults which emerged from each host were also exposed to parasitism in a multiple-choice test for up to an additional generation. Moreover, in olfactometer "Y," the behavior of innate and experienced T. podisi females to volatiles from hosts' egg extracts was tested, to study their learning and memory ability. The original host had influence on T. podisi parasitism; however, T. basalis always parasitized more N. viridula eggs independently of its last rearing host. Innate T. podisi females responded positively to E. heros and P. guildinii egg volatiles, but this behavior was not observed in N. viridula. When T. podisi females were experienced on egg volatiles from a new host, they showed significant learning and memory ability for the specific host volatile for, at least, 24h. Experienced wasps responded positively to N. viridula and through this result we have evidences about the possibility to manipulate wasp's preferences to a specific target host.

Evaluation of the resistance of Coffea canephora to Oligonychus ilicis (Acari: Tetranychidae) and the preimaginal conditioning effect on resistance using a biological life table

ABSTRACTOligonychus ilicis (McGregor) (Acari: Tetranychidae), is one of the most important mite pests found in coffee plants. One way to reduce intensive pest attacks is management via resistant plants. The purpose of this study was to evaluate the resistance of 14 C. canephora genotypes to O. ilicis by antixenosis and antibiosis mechanisms and to determine the preimaginal conditioning effect on resistant genotypes using O. ilicis reared on C. canephora. Resistance by antixenosis was not found; however, nine genotypes showed resistance to O. ilicis via an antibiosis mechanism. Two of these resistant genotypes showed a more persistent resistance than the O. ilicis reared on C. canephora, which indicated that a previous host can affect the selection of a genotype by O. ilicis. The study may provide a model to evaluate the preimaginal conditioning effect on plant resistance, which can be useful for plant breeders.

Host Preferences of Telenomus podisi (Hymenoptera: Scelionidae): Parasitism on Eggs of Dichelops melacanthus, Euschistus heros, and Podisus nigrispinus (Hemiptera: Pentatomidae).

Successful biological control requires detailed knowledge about host preferences of the released parasitoid, because the presence of alternative hosts may affect the control of the target pest. The objective of this work was therefore to evaluate host preferences of Telenomus podisi Ashmead among the eggs of three stink bug species: Dichelops melacanthus Dallas, Euschistus heros Fabricius, and Podisus nigrispinus Dallas (Heteroptera: Pentatomidae). Three independent experiments were carried out to study host preferences among the following: (1) E. heros, D. melacanthus dallas, and P. nigrispinus (bioassay 1); (2) E. heros and D. melacanthus (bioassay 2); and (3) D. melacanthus and P. nigrispinus (bioassay 3). A single bioassay (bioassay 4) was carried out to evaluate the egg size of E. heros, D. melacanthus, and P. nigrispinus. Two more bioassays were carried out: bioassay 5 to study the biological characteristics of T. podisi reared on E. heros, D. melacanthus, and P. nigrispinus eggs, and bioassay 6 to study the morphological characters of T. podisi reared on those different host eggs. Overall, T. podisi consistently preferred eggs of D. melacanthus to those of the other studied hosts, due to probably their better nutritional value; hypothesis that is supported by the fast T. podisi development and bigger parasitoids when reared on D. melacanthus and P. nigrispinus eggs. This allows suggesting that neither pre-imaginal conditioning nor associative learning nor α-conditioning are relevant to T. podisi parasitism. Thus, E. heros eggs could be successfully used for mass rearing of this parasitoid for successive generations since it would not affect its parasitism on other species of the Pentatomidae family in the field.

Influence of host preference, mating, and release density on the parasitism of Telenomus remus (Nixon) (Hymenoptera, Platygastridae)

We evaluated the influence of host preference, mating, and release density on Telenomus remus (Nixon, 1937) (Hymenoptera: Platygastridae) parasitizing eggs of Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). First, we tested host preference of T. remus (free choice test) offered a choice between eggs of Corcyra cephalonica (Stainton, 1865) (Lepidoptera: Pyralidae) and S. frugiperda. Parasitism capacity and host preference (S. frugiperda) of T. remus reared on either of the two hosts did not differ. Secondly, we evaluated the influence of mating behavior of T. remus females on its parasitism. Only the offspring sex ratio differed between treatments, indicating that the species reproduces by parthenogenesis of the arrhenotoky type. Finally, we evaluated the influence of release density on T. remus parasitism. This was tested by releasing different numbers of the parasitoid per S. frugiperda egg using T. remus reared for different numbers of generations on C. cephalonica eggs. The regression analysis between percentage of parasitism and density of released T. remus females showed a quadratic effect for all tested parasitoid generations (F35, F40, and F45) with maximum parasitism from 65.07% to 71.69%. Our results allow the conclusion that (a) T. remus prefers S. frugiperda eggs, regardless of the host on which this parasitoid was reared, showing no preimaginal conditioning; (b) Mating does not affect the number of eggs parasitized by T. remus or the development of its offspring; and (c) The optimal T. remus release density when reared on C. cephalonica is between 0.133 and 0.150 females/S. frugiperda.

Early adult learning affects host preferences in the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae)

Parasitic wasps rely on a hierarchy of stimuli to locate their hosts. Olfactory cues from the natal host complex affect parasitoid preferences and can be learned by parasitoids during larval stages and the early adult stage. While the existence of pre-imaginal conditioning has been documented in several braconid aphid parasitoids, no evidence has yet been provided for parasitic wasps attacking Tephritidae. Psyttalia concolor (Hymenoptera: Braconidae) is a koinobiont larval–pupal endoparasitoid of tephritid flies. In this study, we evaluated the influence of larval and early adult experience on subsequent host seeking in P. concolor females. Parasitoids were reared using Ceratitis capitata or Bactrocera oleae larvae as hosts, and emerging wasp adults were tested for host preferences in two-choice bioassays. P. concolor females preferred to oviposit in, and had higher oviposition success rates on the natal host. When P. concolor females were excised from their host puparia, preventing them from chewing emergence holes, they lost their natal host preference, solidifying the evidence of early adult learning for host selection. This study adds to the growing body of basic knowledge on braconid host-location behavior. From an applied point of view, training procedures for early adult learning has potential for use in mass rearing of parasitoids employed in biological control programs against tephritid flies.

Attractiveness and oviposition preference of Glycaspis brimblecombei Moore in Eucalyptus spp.

The red gum lerp psyllid Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) was first recorded in Brazil in 2003 and since then has caused serious damage in Eucalyptus forests. The damage is mainly due to defoliation, sooty mold and dieback, thus requiring the development of efficient management strategies. The settling and ovipositional preference of G. brimblecombei by species and clones of Eucalyptus were evaluated in free- and no-choice tests. Preliminary tests were done to determine the density of psyllid couples that produced the greatest densities of eggs, leaf position selection for oviposition, and whether oviposition was affected by preimaginal conditioning. Apical leaves were used more frequently for oviposition by the psyllid, and the number of eggs decreased from the apex to the base. The densities of 10 and 15 psyllid couples per seedling produced the highest oviposition. There was no evidence of preimaginal conditioning. In the free-choice test, E. grandis, E. urophylla, VM-1, I-144, C-219 and H-13 were less attractive to G. brimblecombei adults, with H-13, E. grandis and E. urophylla having the least oviposition. In the no-choice test, E. urophylla, GG-100 and E. grandis also demonstrated a lower oviposition, but E. camaldulensis and 3025 were highly susceptible. The low preference for the genotypes E. grandis and E. urophylla suggests the occurrence of a non-preference type resistance against the red gum lerp psyllid. Our results can be utilized for the development of management programs for G. brimblecombei in Eucalyptus forests.

Preferência hospedeira do parasitoide de ovos Trichogramma pretiosum

O sucesso das liberações de Trichogramma spp. depende basicamente do conhecimento das características bioecológicas do parasitoide e da sua interação com o hospedeiro alvo. Assim, o objetivo deste trabalho foi avaliar a preferência hospedeira de T. pretiosum entre os ovos de S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis e A. kuehniella. Para os testes de preferência, foram instaladas arenas com garrafas de polietileno e, em cada uma delas, foi colocada uma cartela com ovos de duas espécies de hospedeiros e uma fêmea do parasitoide por 24 horas. Os parâmetros avaliados foram o parasitismo (%) e a emergência (%). As fêmeas de T. pretiosum apresentaram preferência pelos ovos de A. kuehniella. No entanto, nos ensaios com A. gemmatalis X P. includens e D. saccharalis X S. frugiperda, não ocorreram diferenças no parasitismo. Assim, pode-se afirmar que, nos teste de livre escolha, na ausência do hospedeiro em que os parasitoides foram multiplicados (A. kuehniella), as fêmeas não apresentaram preferência ao parasitismo, o que indica a existência de condicionamento pré-imaginal do parasitoide. Os resultados da viabilidade dos ovos parasitados por T. pretiosum variaram entre os diferentes hospedeiros testados.

Recognition of foreign oviposition marking pheromones is context dependent and determined by preimaginal conditioning

Many insects deposit marking pheromones following egg-laying that signal an occupied and thus sub-optimal resource. Herbivorous insects mark host fruit or other vegetative plant parts after depositing eggs, while insect parasitoids deposit such pheromones directly on the cuticle of a particular life stage of their prey. These oviposition marking pheromones (OMPs) are then recognized by conspecifics, who avoid subsequent egg-laying in the previously utilized and unsuitable host. Since many host resources are capable of supporting a limited number of offspring, these pheromones function to decrease competition among the brood, which increases survival rate of the subsequent generation. In rare instances, distinct species of phytophagous and parasitic insects will inspect the same substrate following egg-laying.1 Recently, Stelinski et al.1 have demonstrated that in such instances, the herbivore is able to learn to recognize its predator’s OMP and utilize it to its advantage by avoiding oviposition into unsuitable host fruit. This recognition of a foreign marking pheromone occurs in a multitrophic context since both herbivore and parasitoid inspect, oviposit into, and mark the same substrate (e.i. fruit surface). In this Article Adendum, we further show that this recognition of a foreign pheromone is both context dependent and mediated by preimaginal conditioning.

Asymmetry of larval diet breadth and oviposition preference inLeptinotarsa undecimlineata

AbstractThe relationship between preference and performance was studied under laboratory conditions for larvae and adult females ofLeptinotarsa undecimlineata(Stål) (Coleoptera: Chrysomelidae).Leptinotarsa undecimlineatafeeds exclusively onSolanum lanceolatumL. (Solanaceae) in the centre of Veracruz, Mexico. A common sympatric species,Solanum myriacanthumDunal, is not used as host. We conducted a series of laboratory experiments to detect reasons for the exclusive use of one host plant.Leptinotarsa undecimlineatalarvae were reared under laboratory conditions on both plant species,Solanum lanceolatumandS. myriacanthum. Length of larval stages, pupal weight, and percent adult eclosion were compared, and larval preference for bothSolanumspecies was tested. Upon eclosion, adult females were exposed to each of the plants, and the effect of larval diet on adult preference was determined. Oviposition on bothSolanumspecies was observed in no‐choice tests. Larvae showed no significant preferences for either plant species. Pupal weight, however, was significantly higher onS. lanceolatum. Female beetles significantly preferredS. lanceolatumleaves, and no effect of preimaginal conditioning was found. Females reproduced in lower numbers after feeding onS. myriacanthum, oviposition initiated later, and females laid fewer eggs than females fed withS. lanceolatum. No female acceptedS. myriacanthumfor oviposition. Results obtained suggest that the potential host breadth ofL. undecimlineatais broader in larvae than in female beetles.

Preimaginal conditioning does not affect oviposition preference in the diamondback moth

Abstract 1. In holometabolous insects, learning has been demonstrated in both larval and adult stages. Whether learning can be retained through metamorphosis from larva via pupa to adult has long been a subject of debate. The present study is designed to distinguish between preimaginal and imaginal conditioning in the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) using oviposition preference tests on females exposed to various types of learning experiences during immature and adult stages.2. Cohorts of test insects were reared from egg to pupa on an artificial diet, or on one of two host plants, Chinese cabbage, Brassica campestris L. ssp. pekinensis, and common cabbage, Brassica oleracea L. var. capitata. The ensuing females reared on the three kinds of food showed similar oviposition preference between the two plants. A brief experience of the less preferred host, common cabbage, by adults slightly increased their preference for this plant.3. Cohorts of test insects were reared from egg to pupa on an artificial diet with or without the addition of a neem‐based oviposition deterrent (Neemix® 4.5). Larval feeding experience did not alter oviposition response to the deterrent. However, emergence conditioning and early adult learning, achieved through experience of a residue of the deterrent carried over from the larval food on pupal cuticle and cocoons, altered oviposition preference significantly.4. The combined results revealed no evidence of preimaginal conditioning in this insect but a strong effect of emergence conditioning and early adult learning on oviposition preference.

Plant volatiles affect oviposition by codling moths

Oviposition in wild codling moth females, collected as overwintering larvae from apple, pear and walnut, was stimulated by volatiles from fruit-bearing green branches of these respective hostplants. Analysis of headspace collections showed that eight compounds present in apple, pear and walnut elicited a reliable antennal response in codling moth females: (E)-β-ocimene, 4,8-dimethyl-1,(E)3,7-nonatriene, (Z)3-hexenyl acetate, nonanal, β-caryophyllene, germacrene D, (E,E)-α-farnesene, and methyl salicylate. Any one of these compounds is found in many other non-host plants, and host recognition in codling moth is thus likely encoded by a blend of volatiles. A large variation in the blend proportion of these compounds released from apple, pear and walnut suggests a considerable plasticity in the female response to host plant odours. Wild females, collected as overwintering larvae in the field, laid significantly fewer eggs in the absence of host plant volatiles. The offspring of these females, however, reared on a semi-artificial diet in the laboratory, laid as many eggs with or without plant volatile stimulus. Tests with individual females showed that this rapid change in oviposition behaviour may be explained by selection for females which oviposit in the absence of odour stimuli, rather than by preimaginal conditioning of insects when rearing them on semi-artificial diet. Oviposition bioassays using laboratory-reared females are therefore not suitable to identify the volatile compounds which stimulate egglaying in wild females.

The Life and Death of Hopkins' Host-Selection Principle

Hopkins’ host-selection principle (HHSP) refers to the observation that many adult insects demonstrate a preference for the host species on which they themselves developed as larvae. The meaning of HHSP has changed significantly since its first proposal in 1916. This review considers how the meaning of HHSP has changed over time and considers the various mechanisms that could contribute to a behavioral bias for the developmental host. The assumption that HHSP implies that the behavior of adult insects is conditioned by larval experience has resulted in widespread condemnation of HHSP. Despite a great deal of attention, there is still very little convincing evidence for preimaginal conditioning of host choice in insects. But growing evidence indicates that genetic variation in behavior and conditioning during the life span of an adult insect can contribute to a preference for the host on which an insect developed. Insects can acquire adult oviposition or feeding preferences through exposure to chemical residues from the environment of earlier life history stages. The concepts of host races and host fidelity have become familiar and acceptable, while the association of HHSP with preimaginal conditioning has led to a general rejection of the term.

Preimaginal conditioning in Drosophila revisited

During metamorphosis, the nervous system of a holometabolous insect changes significantly. Attempts to demonstrate preimaginal conditioning, here taken to mean the retention of learning through metamorphosis, have given mixed results. We used two behavioural assays (the T maze and trap assay) to see whether a change in adult responsiveness could be induced by exposing Drosophila melanogaster larvae to a conditioning stimulus. There was no evidence for preimaginal conditioning from either assay, but the trap assay demonstrated that menthol contamination from the larval environment on the puparial surface could induce a change in adult behaviour. Exposure of adult insects to this contamination could give the appearance of preimaginal conditioning, when in fact the behavioural induction occurred during the adult stage. Young flies responded less strongly than older flies to the odour cues in both assays. This may explain the apparently contradictory findings of some earlier studies of preimaginal conditioning.

In search of a model system for exploring the Chemical Legacy Hypothesis:Drosophila melanogaster and geraniol

We required an experimental system in which to explore elements of the chemical legacy hypothesis, according to which molecules of environmental chemicals may persist on or in the body or immediate surroundings of larval or pupal insects and influence their habitat preferences in adulthood by affecting the maturation of the chemosensory pathways. Using a purpose-built apparatus which exploited the geotactic and phototactic behavior ofDrosophila melanogaster, we examined the pattern of responses to a range of dilutions of geraniol, a terpene of plant origin. Fruit flies avoided the geraniol at high concentrations. Although attraction at low doses and reduced aversion after larval, pupal, or early adult exposure to geraniol have been reported, we did not find either. Thus, we failed to generate the phenomenon described as "pre-imaginal conditioning" required for the model system. We discuss the results in relation to designing suitable assays for testing the Chemical Legacy Hypothesis.

Structural, Behavioral, and Physiological Adaptations of Bees (Apoidea) for Collecting Pollen

Bees, like their wasp relatives, forage for and transport food to a nest as provisions for their offspring. Unlike female Sphecoidea which transport arthropods one at a time as prey, bees transport pollen requiring specialized scopal (brush) or corbicular (fringed plate) structures to transport the dustlike material externally. Scopae often exhibit further modifications in density and amount of plumosity in relation to the size and ornamentation of the pollen grains they transport. Bees also differ from sphecid wasps by possessing branched body hairs that are relatively densely packed. These hairs, the electrostatic surface potential, and specialized hair groups for extraction of hidden pollen are important in the acquisition of pollen from flowers. Structures for grooming (brushes, combs, and scrapers) and grooming behavior patterns are modified to permit manipulation and packing of pollen in the specialized transport structures. The addition of nectar, so that pollen is packed moist, is a behavior that permits the carrying of pollen of a great variety of sizes and ornamentations in relatively simplified scopae or in corbiculae. The addition of oils to the diet of some bees has resulted in a modified type of scopal structure that has a wooly area basally and stiff guard hairs extending distally and that can transport a mixture of oil and pollen. Special hairs on the fore and mid basitarsi and teeth of hind tibial spurs are modified as oil scraper and manipulation structures. The use of corbiculae in Apidae to transport nesting materials and the hind tibiae in male orchid bees (Euglossini: Apidae) for transporting aromatic compounds involves behavior patterns similar to those for pollen transport in grooming, manipulating, and packing the materials. Other behavioral and physiological adaptations important in the location and acquisition of pollen by bees include individual constancy, oligolecty, seasonal synchrony, preimaginal conditioning, daily synchrony, buzz pollination, and other responses to specific modes of pollen presentation. Most of the behavioral patterns involve learning. They may be modified by extrinsic factors, and they may modify intrinsic structural and physiological characters.

Determinants of host selection for species ofAphytis(Hymenoptera: Aphelinidae), parasites of diaspine scales

Host selection behavior in entomophagous insects is a series of reflex responses to physical and chemical stimuli. It was known that the host selection process for Aphytis, parasites of armored scales, utilized the stimulus of a water-soluble chemical contained in the scale cover and that physical features were unimportant. It was unknown whether the adult could exercise host discrimination and restrict oviposition to host species that were suitable for progeny development. When given no choice of host species, the female is under physiological pressure to oviposit and does not discriminate. However, when a choice is present the female prefers to oviposit on the suitable host, though discrimination is not absolute. Suitability is determined by stimuli perceived both by the antennae and by the ovipositor, neither having predominant importance. The scale molt stage is rejected as an oviposition site because of its hard condition, not because of a lack of an “air space” stimulus occurring between the cover and the body. With the cover removed, the second instar scale will continue development to the second molt stage. In that stage, it is free from the host fruit and can be transferred to another fruit where it will become a third instar, forming an entirely new cover. Quick-frozen and defrosted hosts are readily accepted, showing that a movement stimulus or indeed the living condition is not necessary for oviposition. Pre-imaginal conditioning may or may not occur, depending on the species of host. Such conditioning would not be a factor in mass rearing programs using A. melinus. While ovipositing, Aphytis injects a venom into the host, preventing sclerotizing or molting. This prevents loss of the parasite egg due to host ecdysis.